The physical laws of the universe

It is assumed the physical laws apply universally, from the very small to the very big. But do the constants, used in equations, change at the extremes? Michael Murphy's group uses quasars as a background light source, allowing light to be traced as it travels through space. This is used as a backdrop to study galaxies 10 billion light years away. Quasi stellar objects are super massive black holes, billions of times the mass of our sun. They suck in all material around and shine very brightly.

Transcript

Robyn Williams: And if you can't immediately find the Holy Grail in the interstices of the nano world. Why not look out to the mega zone instead? Same universe, same physics...or is it? What if you're a zillion light-years from Earth? Could it be that there physics is as shambolic as Sydney traffic because it changes from place to place and from big to small? Michael Murphy is at Swinburne University.

Michael Murphy: Of course there is always that nagging question...well, you know, those experiments used to establish those laws were only done in laboratories over human timescales, so maybe we should try to do experiments over much longer timescales. Things like the history of the universe is about 14 billion years old, maybe that's a relevant timescale. So maybe the constants change over that period of time. We certainly have found evidence of this. Certainly on the very small scales in the laboratory we know that the constants of physics change, but in a way that we know how to predict, that's completely consistent with our current theory. What we're looking for are changes in the constants or the laws of nature which are outside of that standard model which really can't be explained by our current understanding.

Robyn Williams: Where do you look?

Michael Murphy: Our pet subject is to look as far away as we possibly can. So we try to use quasars. They're incredibly interesting objects in themselves and a lot of people study them, and we just use them as a background light source, a beacon of light through the universe that allows us to trace what's going on as that light comes to us. So we tend to look at galaxies in silhouette against the background quasars and study the fundamental physics in those distant galaxies. These are galaxies about ten billion light-years away, so almost as far away as we can see.

Robyn Williams: Quasi stellar objects; what are they actually?

Michael Murphy: Yes, it is, as I say, an interesting topic in itself. These things really are probably super-massive black holes, and by 'super' I mean billions of times the mass of our own sun. These things reside probably at the middle of the centres of distant galaxies, and there's so much stuff (gas, stars, dust) falling into these objects, they're so dominant in their galaxy, that they just suck in all the material, and as it falls in it glows incredibly brightly. And to us it just looks like a star, that's why it's called a quasi stellar object, people thought they were stars initially, but when they looked more closely at the spectrum of these objects they realised that in fact these were nothing like stars, these were incredibly violent phenomena, and whatever was causing this glow was truly an incredible happening.

Robyn Williams: Could you just explain why it is that a black hole which by definition is black would glow, have light come out?

Michael Murphy: Yes, so the glow that we see is not coming from the black hole itself, it's coming from the stuff falling into the black hole. So when it is falling in, it's crashing into all the other stuff that's falling in, so it really glows incredibly brightly. It's extremely hot. And so there's a lot of radiation coming out from that region around the black hole. The black hole itself is extremely tiny, smaller than our solar system, and emission coming from it is outside that region. But it's still small enough that it represents just a tiny very fine pinprick through the universe that we use to trace along the line of sight to that quasar.

Robyn Williams: So they're places where you do your exploring in terms of theoretical physics. Have you found anything much recently about the ways in which the rules of the universe do change in that far distant place?

Michael Murphy: Yes. Probably in 2003, 2004 we published a very large sample of spectroscopic studies of these quasars, and in these spectra you notice that some colours of the quasars are missing, and that means that there's actually something in front of the quasars absorbing that light, but only in very specific colours, sort of like a barcode. That barcode of absorption tells us something about the physics in the galaxy that's doing the absorption in front of the quasar. So we've actually found that electromagnetism, one of the laws we know and love here on the Earth, seems to be a little bit weaker in distant galaxies. That of course is a very fundamental finding, if correct.

Robyn Williams: It's one of the four fundamental forces, isn't it.

Michael Murphy: That's right. You've got gravity, which we all know unfortunately most of us, but electromagnetism is really the only other force that you'll come into contact with on a day-to-day level. It stops you falling through the floor, it holds molecules together, it relays the sound that you're hearing right now. The other forces are nuclear forces that you don't really come across in everyday life. But if electromagnetism was different in these different galaxies, we simply don't understand why that is, that possibility is not within our current understanding. And if it's correct (and that's a big 'if') then we really have to reformulate physics itself.

Robyn Williams: In fact that's what I was going to ask you because in this era of astronomy, 400 years since Galileo, it's somewhat embarrassing that the laws of physics are, putting it frankly, in a mess. There are so many black holes of understanding, you're really looking for something fundamental to come along to sort it all out, aren't you.

Michael Murphy: That's right, and that's why we have these big experiments in the Large Hadron Collider. These are all aimed at a deeper understanding of the physics, and trying to look into those little black holes of understanding that you mentioned, trying to peer through a little window into the new physics that we think exists there, we think there's an underlying set of physical laws that we're just missing at the moment that brings all of those four forces of nature together into one simple unified law. That's kind of the Holy Grail of physics at the moment. And part of the motivation for doing this work with quasars is that maybe it's best not to look in Large Hadron Collider, maybe it's best to look on much larger timescales in the universe...

Robyn Williams: Especially as they can't get it going yet.

Michael Murphy: They will. It's a bit embarrassing that they haven't, but this is an enormous experiment. If any one of us tried to do it, it would be much more embarrassing. But looking on all sorts of timescales and distant scales in the universe I think is important when you're trying to address these fundamental questions. It's actually remarkable that we can do fundamental physics with astronomy, which it's only in this century that astronomy has really become a proper science in the sense that you can make reproducible observations.

Robyn Williams: When will you know you've got it right?

Michael Murphy: That's a good question. We are at the moment basically repeating our experiment on a different telescope that we have been using in Chile, that's called the Very Large Telescope. The other telescope we used in the past was the Keck telescope in Hawaii that actually at Swinburne we have some access to now. So we're actually trying to compare the data now between the two telescopes and try and understand whether it's something about the telescopes themselves that is leading to this very strange result or whether it's really correct. Of course if we find the same result, I don't think anyone will believe us even then. We really have to go and do this with many other experiments because it is such a fundamental result. Extraordinary claims require extraordinary evidence, and certainly the evidence at the moment is good and strong but it's not extraordinary.

Robyn Williams: And when you have got it, I presume the world will jump up and down like...I wonder when they last did that, 1919 I think when the word came back that Einstein had got it right.

Michael Murphy: I guess so, it would be a similar kind of change in our understanding. It would require a conceptual change. Of course Einstein actually understood that change, and if our experimental results are really right that doesn't mean we understand why the fundamental constants are changing, why the laws of nature are different in different places in the universe. That will require I think a much deeper understanding of the underlying set of physical laws that we've all been striving to do. In fact Einstein himself spent the latter part of his life looking for a unified theory. He didn't know about the nuclear forces then, so he was probably doomed to failure, but at the very least it's a very difficult problem.

But we do need some experimental guidance, and that's why the Large Hadron Collider is there, that's why we're doing these experiments with quasars, and there's many other experiments in physics, all aimed at basically trying to punch a hole in physics. And that's maybe something that a lot of people don't understand, is that we're not satisfied just thinking we know everything. We know that we don't know everything and we're tyring to find out what we don't know.

Robyn Williams: Sounds like the Donald Rumsfeld conundrum, doesn't it! Big physics from Swinburne with Michael Murphy, senior lecturer there. Put their findings together with a little physics from the LHC and hope that they match.